Selecting the right window treatments for each season can make a significant difference in your home's appearance and comfort. Thermal curtains are great for keeping your home warm in winter, but what about summer?
For year-round energy efficiency, it’s essential to select the right window treatment for each season. Here's what you need to know to stay cool in the summer without sacrificing style or function.
How Do Thermal Curtains Work?
Thermal curtains insulate by adding dense layers of fabric—or fabric bonded to foam—that resist heat transfer. The thicker the curtain, the more effectively it blocks heat loss or gain.
When you pull the panels closed, the fabric rests against the window frame and overlaps the walls slightly, sealing the tiny gaps where air usually leaks. This barrier slows drafts that sneak through window joints and door edges, so outdoor heat or cold stays outside.
Do Thermal Curtains Work in Summer?
Thermal curtains are commonly used to retain heat in the colder months, but they’re also surprisingly effective in summer. Their layered construction helps block solar radiation and reduce the amount of heat entering through windows, keeping indoor temperatures more stable even during peak sunlight hours.
According to the U.S. Department of Energy, properly installed light-colored thermal or insulated curtains can reduce heat gain by up to 33% in the summer. This makes them a practical choice for year-round energy efficiency, not just a winter solution.
That being said, the critical factor in summer performance is color. White thermal curtains and other light colored curtains, such as Ivory or beige, reflect more sunlight than darker fabrics. This reflective quality plays a significant role in minimizing indoor heat buildup.
Why Does the Window Placement Matter?
Beyond curtain color, window placement plays a significant role in how much heat enters a room. Unlike doors, which are often shaded or used less frequently, windows are the main entry point for solar heat, especially when they face the rising or setting sun.
East-facing windows receive strong sunlight early in the morning, while west-facing windows are exposed to the sun during the hottest part of the afternoon. If thermal curtains are left open during those times, much of the sun’s heat will already be inside before the curtains are closed.
To be effective, curtains should be drawn before direct sunlight hits the glass. This prevents heat buildup and allows the insulated layer to reflect or block solar radiation before it penetrates the space. Knowing your home’s orientation—and adjusting curtain use accordingly—is a simple yet important step toward keeping rooms cooler and more energy-efficient.
Can Thermal Curtains Completely Cool off a Room?
Thermal curtains are highly effective at reducing heat gain, but they won’t cool a room on their own. Their purpose is to limit the amount of heat that enters through windows, rather than acting as a substitute for active cooling systems like air conditioning or fans.
Used correctly, however, they can significantly ease the burden on your cooling system. In controlled tests, well-insulated window coverings have been shown to cut solar heat gain by as much as 77%, depending on fabric type, fit, and timing of use. That level of reduction makes a measurable difference, especially when you’re trying to keep cooling costs under control.
For optimal results, thermal curtains should be part of a comprehensive cooling strategy—used in conjunction with well-sealed windows, proper ventilation, and an efficient HVAC system. When combined, these measures can keep rooms cooler, reduce energy use, and maintain comfort more effectively than any single method alone.
Can Thermal Curtains be Used Outside?
In outdoor spaces like pergolas, pavilions, or sunrooms, curtains can add comfort by blocking harsh sunlight and providing privacy. While fans or other mechanical cooling methods may disrupt the feeling of being in nature, curtains provide a passive and aesthetically pleasing solution.
Thermal curtains can technically be used outdoors, but they aren’t always the most practical choice. These curtains are heavier than standard outdoor fabrics and typically require sturdy rods or mounting systems designed to support the extra weight. In open-air structures like pergolas or gazebos—where there’s no insulation and plenty of airflow—the insulating benefit of thermal curtains is limited.
However, in semi-enclosed spaces like sunrooms or greenhouses, thermal curtains can be more effective. They help regulate temperature when installed over large windows or glass walls. If the ceiling is made of glass or transparent panels, keep in mind that heat will still enter from above; therefore, a comprehensive solution may require overhead coverage as well.
How Much Do Thermal Curtains Save?
Standard curtains can reduce heat loss by about 17% simply by limiting airflow and trapping indoor air. Thermal curtains take it a step further—thanks to their multi-layered insulation, they can reduce heat transfer by an average of 25%, depending on the fabric density and installation.
With high-quality, tightly woven or heavy duty thermal insulated curtains, that number can reach up to 35%, especially when the curtains are properly fitted and drawn during peak sun exposure or cold drafts.
Over time, this improved insulation translates into lower energy use for both heating and cooling systems, helping to cut down utility costs while keeping your home more comfortable throughout the year.
Why is the Use of Thermal Curtains Important Throughout the Seasons?
Thermal curtains aren’t just for winter. Whether you're trying to retain warmth during cold months or block summer heat from windows, these curtains help maintain a more stable indoor temperature across all seasons.
By reducing drafts and limiting heat exchange through windows and doorways, thermal curtains minimize energy loss and reduce the workload on heating and cooling systems. This makes them a simple, effective way to improve comfort and lower energy costs throughout the year, without relying solely on mechanical systems.